Abstract
To better understand the mechanism of phytochrome-mediated signaling, we used a basal land plant, the liverwort Marchantia polymorpha L. M. polymorpha has a single phytochrome gene, MpPHY, of which product, Mpphy, shows red/far-red photoreversibility in vitro. It has been also shown that a single amino-acid substitution in Mpphy, MpphyY241H, eliminated photoreversibility. In WT, red light inhibited cell elongation and promoted cell division after spore germination, rhizoid formation and regeneration of thalli, while far-red light canceled the effects. In transgenic plants expressing MpphyY241H, formation of rhizoid and constitutive thallus regeneration were observed regardless of light condition. Unlike WT, RNAi line of MpPHY showed transition to reproductive phase in a far-red independent manner. These results indicate that Mpphy regulates photomorphogenesis throughout the lifecycle in M. polymorpha, and that M. polymorpha can be a model plant for analyzing signaling mechanism mediated by phytochrome.